JP2005317372A - Glass-like carbon structure and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glass-like carbon structure having a space inside, which has very little possibility of leakage of fluid even if fluid is passed in the internal space by using it as a separator for a fuel cell or the like. <P>SOLUTION: The glass-like carbon structure with a space inside has a thickness spot of 100 μm or less. In the manufacturing method, a liquid thermosetting resin is coated on a structure consisting of thermosetting resin hardened substance and a jointing layer is formed, and a structure consisting of other thermosetting resin hardened substance is pasted and jointed, then the junction obtained is calcined and carbonized to make the glass-like carbon structure. Coating of the above liquid thermosetting resin is carried out by a screen printing method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is excellent in obtaining a glassy carbon structure having an internal space and a glassy carbon structure having a small thickness unevenness, and after joining the thermosetting resin structures to each other and firing and carbonizing. The present invention relates to a manufacturing method capable of obtaining a simple joint.

  Glassy carbon is a kind of carbon material obtained by carbonizing and baking a cured product of a thermosetting resin, and is glassy and has a very homogeneous and dense structure. In addition to conductivity, chemical stability (especially acid resistance) and heat resistance, which are the characteristics of general carbon materials, it also has the characteristic that the surface of the material does not pulverize and fall off. Has been.

  Glassy carbon has the above-mentioned excellent characteristics, but is difficult to cut. Therefore, a glassy carbon structure having a complicated shape is generally obtained by firing and carbonizing a molded body molded by press molding or injection molding. However, in these methods, it is very difficult to form a complicated shape inside the glassy carbon structure. Therefore, when a complicated shape is formed inside, a bonding layer is formed by applying a thermosetting resin to a structure made of a thermosetting resin cured product, and another thermosetting is formed on the surface on which the bonding layer is formed. A method of bonding and bonding the structures made of the cured resin, followed by firing and carbonization is employed.

  A method for applying a resin material to a resin structure is disclosed in Patent Document 1 and the like. In this method, the resin is applied with a brush or spray gun, but after dividing the coated surface of the resin substrate surface and the non-coated surface, it is necessary to mask the non-coated surface, which is very troublesome in the coating process. There is a problem that it takes. In addition, in these methods, since it is difficult to make the thickness of the coating layer the same on all coated surfaces, uneven coating is likely to occur, and in the case of bonding, there is a problem of inducing bonding failure. .

  In addition, when applying by spraying, the viscosity of the resin material to be applied needs to be low, but in this case, problems such as dripping of the resin material after application from the application surface of the resin structure occur. .

  As another method of applying a resin material to a resin structure, there is a method using a roll coater. However, since the resin material to be applied is applied even to a portion that does not need to be applied, there are through holes in the resin structure. In addition to problems such as clogging holes and dripping inside the holes, the resin material is wasted and uneconomical.

  In addition, in the method using a dispenser, uneven coating tends to occur, and in order to spread the resin material over the entire coated surface, after the resin base material is pasted, it is moved (rubbed) back and forth and left and right to rub. Etc. are required. However, even if such a scrub method is used, it is difficult to make the coating thickness uniform and constant, and since the coating thickness varies depending on the individual, the thickness unevenness of the glassy carbon structure and the thickness in each structure There was a problem that the difference of. Furthermore, when the coated surface is wide, it takes a long time for coating, so it is unsuitable for applying a large amount of resin material.

JP 2000-128602 A

  In view of such a situation, the present invention provides a glassy carbon structure having a small thickness variation having a space inside, and an adhesive layer when such a structure is obtained by firing carbonization of a resin joined body. The present invention relates to a forming method.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by applying a liquid resin using a screen printing method, and have reached the present invention.

That is, the gist of the present invention is as follows.
(1) A glassy carbon structure having a space inside, wherein the thickness unevenness is 100 μm or less.
(2) The glassy carbon structure according to (1), which is a fuel cell separator.
(3) A liquid thermosetting resin is applied to a structure made of a cured thermosetting resin to form a bonding layer, and a structure made of another cured thermosetting resin is formed on the surface on which the bonding layer is formed. A method for producing the glassy carbon structure according to (1) or (2) by firing and carbonizing the obtained joined body after bonding and bonding, and applying the liquid thermosetting resin by a screen printing method The manufacturing method characterized by performing by.
(4) The production method according to (3), wherein the viscosity of the liquid thermosetting resin is 1 to 100 Pa · s.
(5) The production method according to (3), wherein the liquid thermosetting resin contains 0 to 60% by mass of a filler.
(6) The production method according to (5), wherein the filler has an average particle size of 50 μm or less.

  Since the glassy carbon structure having a space inside obtained by the present invention has a good joint portion, even when the fluid is passed through the inside space using, for example, a separator for a fuel cell, the fluid leaks out. Concerns are extremely small, the temperature control of the fuel cell by the fluid can be performed efficiently, and the number of maintenance and the like can be reduced. In addition, since the glassy carbon structure of the present invention has a very small thickness variation of 100 μm or less, when used as a fuel cell supporter, the contact resistance with other fuel cell parts in contact with this separator should be reduced. And the power generation efficiency of the fuel cell can be increased.

  Moreover, according to the manufacturing method of this invention, the said glassy carbon structure can be manufactured with sufficient productivity.

  Hereinafter, the present invention will be described in detail.

The glassy carbon obtained by the production method of the present invention is also called amorphous carbon, and is hard and amorphous carbon showing a shell shape with a black appearance and glassy appearance, and a glossy surface. It is obtained by carbonizing and baking a cured product of a thermosetting resin. This material has excellent characteristics that the surface of the material is not pulverized and dropped off, in addition to the characteristics such as conductive performance, chemical stability, heat resistance, and high purity, which are characteristics of general carbon materials. As general characteristics of glassy carbon, the density is 1.45 to 1.60 g / cm ³ and light weight, and the bending strength is 50 to 200 MPa, and the strength is strong and resistant to acids such as sulfuric acid and hydrochloric acid. There is. As for conductivity, specific electrical resistance is 4 to 20 × 10 ⁻³ Ωcm, and gas permeability is very low as 10 ⁻⁹ to 10 ⁻¹² cm ² / s.

  Glassy carbon has the above-mentioned excellent characteristics, but it is difficult to cut. Therefore, in order to form a complicated shape inside the structure, it is generally a structure made of a cured thermosetting resin. Are bonded with a thermosetting resin, and this is baked and carbonized.

  The thermosetting resin is a resin that, after creating a desired shape by melt molding or the like, is heated to cause a thermosetting reaction, and does not melt by heating. For example, a polycarbodiimide resin, a phenol resin, Examples include furfuryl alcohol resin, epoxy resin, cellulose, urea resin, melamine resin, unsaturated polyester, and aromatic polyimide. In addition to these simple substances, copolymers and mixtures can be used. Moreover, you may add modifiers, such as a crosslinking agent, to these. Among the above resins, the phenol resin is preferable because it is industrially produced as a molding material and is easy to obtain and has a high carbon content by calcination carbonization.

  Further, the thermosetting resin can contain, as an additive, a carbon material, another inorganic material, a material that is carbonized by firing, and the like as long as the properties of the glassy carbon after firing carbonization are not impaired. Examples thereof include carbon fiber, inorganic fiber, inorganic powder, carbon black, graphite particles, glassy carbon, or a mixture thereof.

  The method for producing the thermosetting resin structure is not particularly limited, and may be manufactured by using a molding method such as pressure molding or injection molding, or may be cut from a block of thermosetting resin or machined such as cutting. You may manufacture by. From an industrial standpoint such as mass production, it is preferable to form the structure by injection molding or compression molding without subsequent processing.

  The degree of progress of curing in the thermosetting resin structure can be appropriately adjusted by heat treatment, can be molded into the desired shape, and can maintain the shape in the subsequent firing stage. Alternatively, a highly cured product may be processed. The cured thermosetting resin in such a range may be cured to the C stage where the resin is not melted by heat, and is cured to such an extent that the shape does not change as the resin melts. It may be in a state of being cured up to the B stage.

  In addition, to reduce the thickness unevenness of the thermosetting resin cured product structure after bonding, to reduce the thickness unevenness of the bonding layer, and to prevent damage due to pressure application during the curing process, warp, swell, It is preferable to use those having thickness spots of 100 μm or less. In addition, for the purpose of preventing breakage due to pressure application during the curing process, it is preferable that the bending strength of the thermosetting resin cured product measured according to JIS R1601 and JIS R1602 is 50 to 150 MPa and the bending elastic modulus is 20 GPa or less. Furthermore, in consideration of cracks during firing, it is preferable that each of the adherends has a thickness of 5 mm or less.

  A structure made of a cured thermosetting resin is bonded by bonding after forming a bonding layer on the surface of the structure. In the present invention, the bonding layer is formed by a liquid thermosetting resin. It is made by the method of apply | coating. As the liquid thermosetting resin, a liquid resin, a diluent with an organic solvent, a dispersion with water, or the like can be used. Moreover, you may add an above described additive, a crosslinking agent, etc. As the organic solvent, for example, ethanol, methanol, toluene, acetone, phenol, formalin, furfural, methyl ethyl ketone, denatured alcohol, butanol, propanol, isopropanol, or a mixture thereof can be used.

  The kind of liquid thermosetting resin can be selected from the said thermosetting resin group which can be used as a structure. Of these, liquid phenol resins are preferred. Examples of the liquid phenol resin include a resol type obtained by subjecting phenol and formalin to a polycondensation reaction in the presence of an alkali catalyst, and the nonvolatile content thereof is preferably 40% or more. As commercially available products of such resins, Gunei Chemical Industry Co., Ltd. Resist Top, Sumitomo Bakelite Co., Ltd. Industrial Resin PR, Asahi Organic Materials Co., Ltd. AV Light, etc. can be used favorably.

  If the same kind of material is used for the thermosetting resin structure and the liquid thermosetting resin, the ratio of carbonization during firing is the same, so cracks, cracks, and defect points that occur during the firing process Since generation | occurrence | production can be suppressed, it is preferable. Therefore, in the present invention, it is most preferable that both the thermosetting resin and the liquid thermosetting resin forming the structure are phenol resins.

  In the production of the glassy carbon structure of the present invention, a screen printing method is used when a liquid thermosetting resin is applied to form a bonding layer. The screen printing method is a type of stencil printing, which is a printing method using a screen plate for a plate, and is a printing method in which a hole is made in the plate itself and the coating material is rubbed from there. Screen printing uses screen meshes woven with fibers such as silk, nylon, and tetron, or stainless steel wire, and the resin material to be applied is applied to the resin substrate.

  An outline of screen printing is shown in FIG. In screen printing, a plate film (resist) made in advance by handicrafts or optical engineering (photograph) method is used to close the eyes other than the necessary image line, and the screen is tensioned by pulling it on all sides. Let them fix. As the screen plate material, fibers such as silk, nylon, and tetron, or stainless steel and aluminum wire are used. Considering the stretchability of the screen that affects the dimensional accuracy of the coating shape and the corrosion resistance of the screen, Tetron, It is preferable to use stainless steel.

  Next, a liquid resin is placed on one end inside the screen plate, and a squeegee is reciprocated and extruded under the ridge of the screen to apply the liquid resin to the surface of the cured thermosetting resin structure. Since the screen plate is relatively flexible, the same pattern can be accurately and repeatedly transferred regardless of the shape of the thermosetting resin cured product structure and whether the coating surface is complex. .

  Furthermore, since the coating thickness of the liquid thermosetting resin can be determined by the mesh wire diameter and mesh opening, it can be stably applied to the desired thickness, and the thickness unevenness of the structure obtained by bonding after coating can be reduced. it can. Common meshes include those with a wire diameter of 0.04 mm to 0.15 mm, a thickness of 0.08 mm to 0.30 mm, and an aperture ratio of 30% to 45%. However, a high viscosity material such as a liquid resin is applied. In some cases, for example, by using a mesh having a wire diameter of 0.06 mm to 0.12 mm, a thickness of 0.12 mm to 0.24 mm, and an aperture ratio of 32% to 38%, the thickness of the structure obtained by bonding after application is obtained. Spots can be suppressed to 100 μm or less.

  In addition, generally in screen printing, the pressure applied to the squeegee is 20 kPa to 100 kPa, the squeegee angle is 0 degree to 30 degrees, the squeegee speed is 10 mm to 150 mm per second, and the gap length between the mesh and the object to be applied is 1 mm to The coating thickness can be controlled by adjusting within a range of 5 mm. When the coating thickness is 0.05 mm to 0.15 mm using a liquid resin, the pressure applied to the squeegee is 50 kPa to 250 kPa, the squeegee angle is 15 degrees to 45 degrees, the squeegee speed is 50 mm per second to 150 mm per second, and thermosetting is performed. The gap length with the conductive resin structure may be adjusted in the range of 2 mm to 4 mm. It can also be adjusted by the viscosity of the liquid resin to be applied.

  As described above, the screen printing method is easy to control the coating amount, coating thickness, and the like, and is suitable for coating the liquid resin in a complicated shape because the usable liquid resin has a relatively wide viscosity range.

  In the production method of the present invention, the viscosity of the liquid thermosetting resin to be applied at 25 ° C. is preferably 1 to 100 Pa · s, more preferably 3 to 50 Pa · s. When the viscosity is less than 1 Pa · s, the fluidity of the liquid thermosetting resin is high, so that the surface of the cured thermosetting resin structure is repelled and the thickness of the bonding layer becomes uneven. On the other hand, when it is higher than 100 Pa · s, there is a problem that the fluidity of the resin liquid is low and the coating becomes extremely difficult. The viscosity of the liquid resin can be measured by, for example, a commercially available viscometer such as B-type rotational viscometer LVDV-I + manufactured by Brookfield.

  A filler may be blended with the liquid thermosetting resin for the purpose of adjusting the viscosity. The filler is preferably a substance that does not heat and melt, for example, a thermosetting resin cured product, a thermosetting resin carbide, a carbonaceous material such as graphite, carbon black, carbon fiber, carbon nanotube, fullerene, inorganic powder, Examples thereof include inorganic whiskers, cellulose fibers, cellulose powder, wood powder, and mixtures thereof. The blending amount of the filler is preferably 0 to 60% by mass, more preferably 10 to 40% by mass, based on the entire liquid material. When the blending ratio exceeds 60% by mass, thixotropy is increased and application tends to be difficult.

  The average particle size of the filler is preferably 50 μm or less. When the average particle size is larger than 50 μm, the leveling property after coating is poor and unevenness remains on the joint surface, thereby causing bubbles in the joint layer, causing cracks in the firing process and reducing the strength of the structure.

  The structure made of the cured thermosetting resin bonded with the thermosetting resin as described above and having a space inside is subjected to heat treatment for the purpose of drying and curing. The conditions are not particularly limited, but the temperature is preferably in the range of 120 to 250 ° C, more preferably in the range of 130 to 200 ° C. When the temperature is lower than 120 ° C., appropriate curing of the bonding layer is insufficient, and cracks or cracks due to foaming may occur in the subsequent firing step. Moreover, when it exceeds 250 degreeC, the thermosetting resin structure surface will be oxidized and the surface external appearance may be impaired.

  Furthermore, in order to further strengthen the adhesion between the adhesive layer and the structure, it is preferable to apply a pressure to the adhesive surface, and the condition is preferably a pressure range of 5 to 500 kPa, more preferably, It is in the range of 5 to 300 kPa. When the applied pressure is less than 5 kPa, voids may occur in the structure and the bonding layer, or the bonding layer may peel off, and when it exceeds 500 kPa, the spatial shape formed inside the structure is crushed. It may be deformed.

  Next, the thermosetting resin which is joined and integrated and has a structure having a space inside is baked and carbonized to form glassy carbon. Firing is performed under an inert gas atmosphere such as nitrogen gas, helium gas, argon gas, or under vacuum. Moreover, 700-1600 degreeC is preferable and baking temperature is 900-1200 degreeC more preferably. When firing at a temperature of 700 ° C. or lower, sufficient carbonization cannot be performed, so that the characteristics of glassy carbon are not exhibited. On the other hand, even if a temperature exceeding 1600 ° C. is applied, the energy efficiency is lowered because no significant change occurs in the properties of the obtained glassy carbon. The firing time is not particularly limited, but a range of 1 to 10 hours is appropriate.

  The size of the glassy carbon structure that can be produced according to the present invention is not particularly limited, and the design can be changed according to the purpose. For example, a relatively large size such as 300 mm × 300 mm × 3 mmt can be used. It is possible to create a fine and precise one having a plurality of channels having a width of 0.2 mm and a depth of 2 mm inside a 20 mm × 40 mm × 2 mmt, and particularly suitable for the production of a plate-like structure. Yes.

  The thickness variation of the produced glassy carbon structure is preferably 100 μm or less. When the thickness spots are larger than 100 μm, for example, when a glassy carbon structure is used as a fuel cell separator, it becomes a factor of increasing contact resistance.

  Next, the present invention will be specifically described with reference to examples.

In the following examples, the following measurements were performed.
(1) Viscosity of liquid resin: measured at 25 ° C. using a Brookfield B-type rotational viscometer LVDV-I +.
(2) Warpage of thermosetting resin structure before bonding: The surface of the structure is brought into contact with the reference device so that a gap is formed between the center of the surface of the structure and the reference device, and then the reference device and the structure A gap gauge was passed through the gap formed between the body and the thickness of the gap gauge with the maximum thickness that could pass through the gap was evaluated as the warp of the structure.
(3) Waviness of thermosetting resin structure before bonding: Using a waviness measuring device (manufactured by Aptic Co., Ltd.) equipped with a contact-type linear gauge, the waviness of the surface in the thickness direction of the structure is measured, and the maximum The difference between the value and the minimum value was evaluated as undulation.
(4) Thickness unevenness: about the thermosetting resin structure before joining and the structure obtained by firing these after joining, the sum of the groove edge thickness of 8 places on the outer edge and the groove groove thickness of 1 place in the center Nine locations were measured with a contact-type thickness measuring device (manufactured by Aptic Co., Ltd., sensor diameter 0.45 mm), and the difference between the maximum value and the minimum value of the nine thickness data was defined as thickness spots and evaluated. It was.

Example 1
Using phenol resin (Unibex N type manufactured by Unitika Co., Ltd.) as a raw material, using an injection molding machine (80 Ton injection molding machine), the outer dimensions of 122 mm x 122 mm x 2.4 mmt with the groove structure shown in Figs. Obtained two phenolic resin structures. As a result of measuring the warpage, undulation, and thickness variation of each of these structures, the warpage was 50 μm, the undulation was 30 μm, and the thickness variation was 20 μm. A liquid phenolic resin (Gunei Chemical Resist Top PL-4804) having a viscosity at 25 ° C. of 4 Pa · s on the upper surface other than the groove portion of the resin structure of FIG. 3 is a screen printing machine (manufactured by Mino Shoji Co., Ltd.) It applied using the hand-printing press hand printer Type-1 B3) with an adsorption device.

  The screen was made of Tetron mesh count # 80, the squeegee was made of medium-hard rubber, the width was 180 mm, and the thickness was 9 mm. The squeegee angle was 30 degrees, the squeegee speed was 2 m / min, and the gap length was 4 mm.

  The resin structure of FIG. 2 is bonded to the upper part of the resin structure of FIG. 3 coated with a liquid phenolic resin, and joined as shown in FIG. Time dried and cured. Thereafter, firing carbonization was performed for 5 hours at 1000 ° C. in a nitrogen gas atmosphere using a high-performance firing furnace to obtain a glassy carbon structure having a space inside. When the thickness of this glassy carbon structure was measured, the thickness of each part was 3.93 mm-4.01 mm, and the thickness spot was 0.08 mm. The structure was cut using a diamond cutter, and an electron micrograph of the cross section was taken. A photograph is shown in FIG. From this photograph, the bonding layer could not be confirmed. Moreover, peeling, deformation, and destruction of the bonding layer could not be observed. From this observation, it was determined that the entire structure including the bonding layer was glassy carbon.

Example 2
Liquid phenolic resin (Gunei Chemical Industry Co., Ltd., Resist Top XPL-6820B) and phenol resin not heated and melted (Unitika Ltd., Universex C type) were mixed at a mass ratio of 60:40. Using a 50 Pa · s liquid phenolic resin, a glassy carbon structure having a space inside was obtained in the same manner as in Example 1. When the thickness of this glassy carbon structure was measured, the thickness of each part was 3.95 mm-4.03 mm, and the thickness spot was 0.08 mm. In observation of the fracture surface of this structure with a diamond cutter, the bonding layer could not be confirmed, and peeling, deformation, or destruction of the bonding layer could not be observed. From this observation, it was determined that the entire structure including the bonding layer was glassy carbon.

Example 3
Liquid phenolic resin (Gunei Chemical Industry Co., Ltd., Resist Top XPL-6820B) and phenol resin not heated and melted (Unitika Co., Univex C type) were mixed at a mass ratio of 85:15. Using a 5 Pa · s liquid phenolic resin, a glassy carbon structure having a space inside was obtained in the same manner as in Example 1. When the thickness of this glassy carbon structure was measured, the thickness of each part was 3.94 mm-4.02 mm, and the thickness spot was 0.08 mm. In observation of the fracture surface of the obtained structure with a diamond cutter, the bonding layer could not be confirmed, and peeling, deformation, or destruction of the bonding layer could not be observed. From this observation, it was determined that the entire structure including the bonding layer was glassy carbon.

Comparative Example 1
Liquid phenolic resin (Gunei Chemical Industry Co., Ltd., Resist Top XPL-6820B) and phenol resin not heated and melted (Unitika, Universex C type) were mixed at a mass ratio of 60:40. A glassy carbon structure having a space inside was obtained in the same manner as in Example 1 except that a liquid phenol resin of 50 Pa · s was used and applied to the cured resin structure with a brush. The thickness unevenness of the obtained structure was 150 μm. In the observation of the fracture surface with a diamond cutter, the bonding layer was confirmed, and there was a part where it was partially peeled off. In addition, blistering occurred in the appearance, which was insufficient as a glassy carbon structure having an internal space.

Comparative Example 2
Liquid phenolic resin (Gunei Chemical Industry Co., Ltd., Resist Top XPL-6820B) and phenol resin not heated and melted (Unitika Co., Univex C type) were mixed at a mass ratio of 20:80. Using a liquid phenol resin of 150 Pa · s, a glassy carbon structure having a space inside was obtained in the same manner as in Example 1. The thickness unevenness of the obtained glassy carbon structure was 180 μm. Moreover, in the observation of the fracture surface of this structure with a diamond cutter, the bonding layer was confirmed, and there was a part where it was partially peeled. In addition, blistering occurred in the appearance, which was insufficient as glassy carbon having an internal space.

It is the schematic of screen printing. It is a thermosetting resin cured product structure of the present invention. It is a thermosetting resin cured product structure of the present invention. It is the thermosetting resin hardened | cured material structure after joining of this invention. It is sectional drawing of the glassy carbon structure of this invention.

Explanation of symbols

1: Screen frame
2: Screen surface
3: Squeegee
4: Squeegee angle
5: Liquid thermosetting resin
6: Thermosetting resin cured product
7: Gap length

Claims (6)

A glassy carbon structure having a space inside, wherein the thickness unevenness is 100 μm or less. The glassy carbon structure according to claim 1, which is a fuel cell separator. A liquid thermosetting resin is applied to a structure made of a thermosetting resin cured product to form a bonding layer, and another structure made of a thermosetting resin cured product is bonded to the surface on which the bonding layer is formed. Then, the obtained bonded body is calcined and carbonized to produce the glassy carbon structure according to claim 1 or 2, wherein the liquid thermosetting resin is applied by a screen printing method. A featured manufacturing method. The manufacturing method according to claim 3, wherein the viscosity of the liquid thermosetting resin is 1 to 100 Pa · s. The production method according to claim 3, wherein the liquid thermosetting resin contains 0 to 60% by mass of a filler. 6. The production method according to claim 5, wherein the average particle size of the filler is 50 μm or less.